I'm working on a new choke linkage for my carbs at the moment. I need to change a pure linear movement into a rotational one with a very short rod. I had been using brass rods and just letting them flex. I want to go to heavier stainless rods which will require some sort of link. mostly a fabrication problem.

Plaka, unless you just wan't to fabricate some small pieces, check out bell cranks and other actuators for R/C model aircraft. Lots of neat stuff at hobbyshops catering to serious builders and enthusiasts. Should be stuff sized perfectly for choke linkages.

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Mark J
Merritt Island, FL

When a person asks you for advice, they don't want advice. They want corroboration.

Plaka, unless you just wan't to fabricate some small pieces, check out bell cranks and other actuators for R/C model aircraft. Lots of neat stuff at hobbyshops catering to serious builders and enthusiasts. Should be stuff sized perfectly for choke linkages.

I've looked at some. Unfortunately it's not stainless. Appreciate the tip. Might find some model watercraft stuff that will work.

I am going to stay stubborn here and consider gearing and other options for a nicer highway experience. I seriously just want a cruising gear where 70 is hovering at 4-5k RPM. I know the bike will have no guts at the top of 5th or from a dig but I think I can manage. And if not....I will swap it back in an afternoon.

Again, the R65 is NOT an R100. It LOVES REVS. Surely someone has a dyno printout of an R65 vs an R100 in similar tune.

But no matter how hard you try, an R65 WILL NOT drive like an R100 or even an R80. Please believe people when they tell you this.

I think that's the problem with peoples impression of the R65 - they come to it expecting it to be like other BMW twins....and it doesn't match expectations. For me I come to it from 650 2 valve pushrod twin experience - and for a engine of that type in the high 40's to low 50's HP range it stacks up pretty well...a little overweight, but smooth with stable handling.

My concern using a silicone pan gasket is the bolts falling out. There's no way the bolt will bind in the hole with the gasket being soft and squishy. Do you use loctite? Those suckers fall out easy enough with the stock hard one.

Bolts don't fall out but the gaskets to feel too soft (I'm using two). Didn't leak but I'm replacing them with paper. Just didn't like the feel of the silicone. No, never fell out but it was just worrisome. No locktite but did use a skim of ultracopper with the gaskets and that extruded into the bolt holes and hung them up.

is there an "autoparts store" replacement for a headlight relay on a 78 R80/7? the originals aren't terribly expensive, but was hoping i didn't have to order one and wait around for it.

As best I can tell the "headlight relay" is actually a load shed relay for the Always-on headdlight bikes. Kills the headlight when you hit the starter. I put a switch on my headlight so just ditched the "headlight relay" and redid the wiring. No ill effects. I do have actual power relays on the headlight so it isn't drawing through the switch.

I would only use the factory relay unless you cut your old one open and confirm a circuit you can get out of a stock auto store (power) light relay.

The shorter rod is lighter but for a given crank throw, works through a greater angle which costs mechanical efficiency. The hevier longer rod works through less angle, but makes the cylinder a lot longer. Steam engines use very long rods and run them externally to the cylinder. So the cylinders can be short and they are just located a couple feet behind the crank/flywheel. The rods are sometimes double jointed (like a gas engine but externally). Other times the entire cylinder swings. look at some pics of old trains to see the various layouts.

I'm working on a new choke linkage for my carbs at the moment. I need to change a pure linear movement into a rotational one with a very short rod. I had been using brass rods and just letting them flex. I want to go to heavier stainless rods which will require some sort of link. mostly a fabrication problem.

Shorter rods make better mechanical efficiency, not less. The main advantage of longer rods is the different piston movement per crank rotation. Different length rods drastically changes the relationship of piston movement compared to crank movement. Shorter rods work well for low rpm and longer rods work well for higher rpm. Airheads already have a comparably long rod at 1.91:1. Longer rods (around 2.15:1 rod length ratio) via higher piston pin bores, not longer cylinders, increases torque and hp above around 4000 rpm because the pistons have more TDC dwell time.

HD XR750's have around 2.15:1 rods. One of their secrets in making so much high rpm torque. After making them run smaller and smaller intake restrictors for four seasons I believe (three of the seasons in a row), modern OHC 1000cc engines are beginning to keep up.

Working with a lightly modified 302 and changing nothing but the pistons/pin location they found that long rods worked better everywhere.

Their reasoning was that with long rods the piston spent a shorter time at TDC , then moved away from TDC slower.
So it was still to catch more of the pressure build up, and at the point where it could make most use of the pressure, when the angle between rod and the crankpin radius was around 90 degrees, the piston was further up the bore and subject to more pressure.

All made sense to me, and of course the cams and possibly ignition timing could also be optimised to suit the longer rod too, putting it further ahead.

But that is their opinion, and their results, and if anyone has a logical explanation as to why shorter rods work better, and some documented test results I am certain we would all like to hear them.